在Scala中扩展对象实例的类

Question

Say I have an instance of a class that has many methods and I want to extend the behaviour of say one method in that object. In java I guess I would have to create a wrapper that redirects all calls to the instance and I could then redefine the relevant method in the wrapper. But I was wondering if in scala there was some other cleverer way to do this?

so eg

class A {
  def x = 1
  def y = 2
  def z = 3
}

val a = new A

val a2 = wrap(a) { override def z = 4 } // ???

Regards Des

Answer 1

In Java we have the ability to extend an entire class. It is up to the programmer to decide which methods become overridden. We use the "extends" keyword to perform this task.

ie

public class A
{
  public void method1(){...}
  public void method2(){...}
}

public class B extends A
{
  public void method2(){...}
  public void method3(){...}
}

Here for class B we use the extends keyword. Due to inheritance, class B inherits method1, and in this case overwrites method2 and has added another method called method3. Hope this helps.